Philip Hammond has accused the SNP government of deliberately keeping Scots in the dark about the effect independence would have on Scotland’s defence, saying it would be devastating for families reliant on the sector for jobs.

The defence secretary delivered the gloomy prediction in what was billed as a positive speech about the Union yesterday. He was speaking to employees at Thales, the Glasgow-based company that manufactures periscopes for submarines, and was accused by one worker of being “quite threatening”.

The “no” campaign has been criticised for its negativity and the polls tightened after a string of business leaders warned